Clay beneficiation



3,970,544 CLAY BENEFKCEATION Wiiliarn R. Johnson, Texas City, and David T. Bakes,

Dickinson, Tern, assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Nov. 21, 1960, Ser. No. 76,395 It Claims. (ill. 2528.5)

The present invention relates to the treatment of clays and, more particularly, to the beneficiation thereof by chemical treatment to render them especially useful in the production of Well drilling muds.

Drilling of an oil or gas well by the rotary method is performed by rotating a bit attached to the end of a hollow drill pipe, known as a drill stem, which extends downwardly through the well bore. As the drill stem is rotated from the surface, the bit cuts or grinds away the formation into small fragments known as cuttings which must be removed from the hole in order that the drilling may progress. To carry away these cuttings, a fluid commonly referred to as drilling mud is continuously pumped down the drill stem, through channels in the drill bit itself, and then up through the annular space between the drill stem and the walls of the borehole to the surface of the earth. In additionto the primary function of picking up the cuttings produced by the drill bit and carrying them to the surface, the drilling mud serves a number of other purposes. It must lubricate and cool the drill stem and bit; it must apply a hydrostatic pressure to the formation to counterbalance the pressure of any liquids or gases which may be encountered in the various strata penetrated by the drill bit in order to prevent flow of formation fluid into the bore hole; and it must form on the walls of the borehole a thin impervious layer or sheath of solid material which serves to reduce loss of water from the borehole to the formation and provides support for the walls to prevent their collapse into the drill hole.

- Drilling fluids or muds of this character are usually prepared from clay or commercial mud bases having gel-forming characteristics. Clays suitable for this purpose are of two general types: Wyoming or bentonitic clays and native or sub-bentonitic clays. The choice of a particular clay insofar as mud preparation is concerned depends upon its yield value. The yield of clay is defined as the number of barrels (42 gallons per barrel) of aqueous dispersion or mud having a viscosity of 15 centipoises which can be prepared from a ton of clay. Generally speaking, a yield of at least 96 barrels of l-centipoise mud per ton of clay is the minimum standard for acceptable material. Such a yield can be expected with the purer forms of sodium bentonite such as Wyoming bentonite but is not attained with less pure forms or with the calcium and other metaand sub-bentonites. laboratory testsmade with typical clays of the bentonitic and sub-bentonitic jtypes have shown that a-yield of anywherefrom 50 to 100 barrels is obtainable with the former types while the latterlproduce only from 25 to 50 barrels. because oftheir superior yields some of these even do not come up to the required standards. There is aneed, therefore, for increasing the yield obtainable from both the low-yield bentonitic clays and the sub-bentonitic clays so as to increase their utility as mud-making materials and make them competitive with Wyoming 'bentonite. Also, there are distinct advantages to be gained in further up-grading of socalled high-yield clays. Great economies can be effected, for example, if the yield can be doubled so that only half the amount of clay is required to prepare a given quantity of high quality drilling fluids. Too, a mud of low-solids content gives faster Actual- Thus, while the bentonitic clays are preferred States atent drilling rates and thus lowers appreciably the cost of drilling a well.

Attempts have been made to up-grade the low-yield clays but such attempts have been generally without success. One method widely used has been to add to the clay a peptizing agent such as soda ash or sodium carbonate. This method of base exchanging the calcium ions with sodium ions has not always been successful by any means probably because the base exchange cannot be forced to completion in a practical manner and the slight improvement achieved is not economical.

Accordingly, it is an object of the present invention to provide a method for beneficiating a clay either of the bentonitic or sub-bentonitic type so as to increase its yield.

It is a further object of the invention to provide a method and means for improving the mud-forming characteristics of clays used to make well drilling muds and more especially for increasing the yield of mud obtainable from such materials.

Another object of the invention is to provide a composition for use in making drilling muds whereby higher yields of mud are possible than could be obtained heretofore from raw materials of the same quality.

' Other objects and advantages of the invention will become apparent from the following description thereof. In accordance with the invention, the yield of a clay is increased by treating said clay With a water-soluble interpolymer comprising substantially equimolar portions of maleic anhydride and an olefin having from 2 to 4 carbon atoms and diallyl other in an amount in the range from about 0.1% to about 5.0% by weight based on the reacting monomers. Particularly preferred are the interpolymers of ethylene, maleic anhydride and diallyl ether. 5 The interpolymer beneficiating agents can be added to the clay in any desired manner. In general, a simple mechanical mixture of the clay and polymer treating agent is prepared by dry-blending the interpolymer in powder form directly with dry clay. This can be done conveniently at the time the clay is ground in a roller mill, for example. Alternatively, an aqueous solution of the interpolymer may be sprayed directly onto the clay either in stock piles, after crushing, during a grinding operation, or during a bag-packing operation. Also, if desired, the clay and interpolymer can be separately added in any desired order to form a slurry. This type of wet mixing, although not preferred, could be employed, for example, at the well site.

The amount of the interpolymers needed for treatment depends to some extent on the degree of beneficiation desired and varies with the clay but generally only very small quantities are required. Amounts within the range from about 0.1 to about 10 lb. per ton of clay will produce satisfactory results. The preferred quantities for treatment are from about 1.5 to 3.5 lb./ton of clay. in general, the yield obtainable at a concentration of 3 lbs. of the interpolymers per ton of clay lies in the range from 160490 barrels. With some clays, yields as high as 195 barrels have been achieved by increasing the concentration to 3.5 lb./ton of clay. In some instances, a maximum yield of barrels is obtained with 1.5 lb. of the interpolymers per ton of clay and further addition results in a decrease in yield value.

The interpolymers useful as clay beneficiating agents are those having a specific viscosity of at least 0.3, it being understood that the specific viscosity value is that determined at 25 C. on a 1% solution (by weight) of the anhydride form of the interpolymer in dimethylformamide. It is diflicult to establish any one preferred range of specific viscosity for the interpolymers since this is a factor which varies somewhat depending upon the paracrobatfor best results together with an alkali metal compound which is water-soluble, ionizable, and ha an anion ca pable of reacting with calcium to form a water-insoluble precipitate. Such compounds include alkali metal carbonates, hypophosphates, oxalates, phosphates, silicates, sulfites and tartrates. Particularly preferred is sodium carbonate or soda ash. The amount of the. alkali metal compound employed will be somewhat dependent upon the proportion of calcium montmorillonites in the whole clay. Generally, amounts from about 1% to about 7% by weight of the clay can be used with increasing amounts giving higher degrees of beneficiation. However, because amounts slightly in excess of 7% can act to reduce the yield of clay, it is advisable in order to secure maximum results and still allow some latitude in operation, toemploy amounts slightly less than 7%. With soda ash, for instance, preferred amounts are those from about 3 to about 7% by weight with optimum results being obtained with about by weight.

The interpolymers used as clay beneficiating agents are readily prepared by polymerizing a mixture of maleic anhydride, a C -C olefin, i.e., ethylene, propylene, nbutylene, and isobutylene,.or olefin mixture and diallyl ether. The amount of diallyl ether employed depends to some extent upon the olefin employed but generally lies inthe rangebetween 0.1 and 5.0% by Weight of the total.

polymerizable mixture. When ethylene is a comonomer, for example, the amount of diallylether added should not exceed about 3.0% in order that the interpolymerpros duced will have the required viscosity. when dispersed in water. With the higher olefins, the amount of diallyl ether can be increased up to the 5% level if desired. Amounts in excess of those specified usually result in the diallyl ether functioning as a chain-transfer agent in the polymerization rather than as a comonomer.

The polymerization is carried out in an inert organic solvent, preferably a non-polymerizing hydrocarbon solvent, having solvating action on the monomers but little appreciable solvent or swelling action on the interpolymer produced. In this way, the polymer is obtained in the form of a fine powder which only requires freeing from solvent before use. Suitable solvents include, for example, ethylene dichloride, ethyl acetate,.dioxane and, particularly, aromatic hydrocarons such as benzene, toluene and xylene.

While the olefin and maleic anhydridereact in sub stantially equimolar proportions, in the usual method for producing the interpolymers, the olefin is employed in excess. The anhydride and the diallyl ether in the desired proportions are charged to the reactor dissolvedv in the solvent and the reactor is. then brought up to the. desired.

pressure by charging the. olefin. Operating pressure is thereafter maintained by continuous charging of olefin throughout the reaction period. The monomers are pref: erablydissolved in an amount of solvent such that the solids content of the reaction slurry formed is about 15%. This ordinarily represents an amount of solvent about six times the total weight of the compounds to be polymerized. The amount of solvent is not critical, however, and proportions of solvent as much as or 20 times the weight of the olefin and maleic anhydride may be used. Alternatively, the diallyl ether may be added to the mixture of anhydride and olefin during the course of the polymerization either over part or all of the polymerization period.

A1 The resulting solution is mixed thoroughly and heated sufficiently so that the polymerization reaction takes place.

An organic solvent-soluble catalyst is necessary. Any of the organic free-radical-catalysts is satisfactory. Among these are various organic solvent-soluble peroxygen compounds including benzoyl peroxide, capryl peroxide, acetyl peroxide, acetyl benzoyl peroxide, di-tert-butyl peroxide the range from 40 C. to C. Pressure may vary from.

atmospheric to about 600 p.s.i.g. or. higher depending upon the particular olefin used.

At the completion of the polymerization reaction, the

interpolymeris recovered from the organic solvent by any' suitable means.

While the interpolymers may be used in the anhydride. oracid form, they are more commonly employed as clay beneficiating agents in the form of their alkali metal or' ammonium salts. Alkali metaljor ammonium salts of the interpolymers sucha'ssodium, potassium, lithium, rubidium and caesiumsalts may be obtained by reacting the.

interpolymers with the stoichiometric amount of. the corresponding hydroxide. Partial salts may, of course, be produced by' using less than the quantity of alkali required to eflect completeconversion of the carboxyl" groups. When polymeric. anhydrides are reacted with'anhydrous ammonia, an appreciable amount of amide groups are formed resulting, in mixed ammonium-amide polymeric salts.

The following examples are. presented to illustrate the invention but are not tobe construed as, limiting it in any manner whatsoever.. The testingprocedure used for.

obtaining yield values for both treated and untreated clays was as follows:

About 10 g. of clay was added to 350 ml. of distilled water alone or to distilled water containing a dissolved mterpolymer of an olefin, maleic anhydride and diallyli ether in the desired concentration and the suspension was mixed in a Hamilton-Beach mixer for 15 minutes. For convenience, a 0.25% aqueous solution of the interpolymers tested wasprepared and' this solution was added to the water using a burette to obtain the desired concentratron.

of the slurry was determined usinga Fann viscosirneter and recorded. The mixture was covered and allowed to' stand for a period of 24 hr. After this aging, the mixture was again subjected to mixing for three minutes in a,

Hamilton-Beach mixer and the viscosity of the slurry was again determined. In. the thermal stability tests, the;

mixture was then subjected to heating at. a temperature of about F. for 72 hr. in an ovenof special design which provided for continuous rollingof. the mud con-1 tainers. Subsequently,' the mixture was stirred for 3 min-.

utes and its viscosity measured. Yield values were estimated from theviscosimeter dial readings by means of graphs prepared from a collection of such readings.

Example 1 Effect of treatment on a sample of bentonite clay commercially availabe from The Milwhite Mud Sales Company, Houston, Tex.

Additive: A composite mixture of interpolymers of equimolar proportions of ethylene and maleic anhydride and 1% by weight of diallyl ether in the sodium salt form having-specific viscosities in the range from 0.68-2.2.-

Two ml. of this solution represented a 1 lb./ton treatment level. Immediately after mixing, the viscosity Additive Viscosity Estimated Viscosity Estimated lb./ton (cp.) (15 yield (cp.) (24 yield min.) (bbL) hr.) (0121.)

Example 1 shows that a commercially produced clay of originally acceptable yield can be significantly upgraded by the interpolymer of the invention.

Example 2 Efiect of treatment on a sample of bentonite clay commercially available from the Baroid Division, National Lead Company, Houston, Tex., under the trade name Aquagel.

Additive: Interpolymer of substantially equimolar proportions of ethylene and maleic anhydride and 1% by weight of diallyl ether having a specific viscosity of 2.82.

Additive Viscosity Estimated Viscosity Estimate 1b./ton (cp.) yield (co) (2!. yield min.) (bbL) hr.) (bbl.)

Example 2 again demonstrates that dramatic increases in yield of so-called good clays can be effected by treating them with interpolymers of ethylene, maleic anhydride and diallyl ether. Here with only 2.5 lb./ton of clay treated, an increase in yield of almost 100% is obtained.

Example 3 Etfect of treatment of a sample of high-yield Wyoming entonite at the 3-lb./ton level.

Additives: Interpolymers of equimolar proportions of ethylene and maleic anhydride and 1% by weight of diallyl ether of various specific viscosities.

Addi- Viscosity Esti- Viscosity Esti- Viscosity Estitive (cp.) mated (cp.) mated (cp. mated 7151p (15 min.) yield (24 hr.) yield (72 hr. at Yield (bbL) (hbl.) 150 F (bbl.)

None 2. 75 95 3. 25 100 Example 4 Effect of treatment on native or sub-bentonitic clay mined in Mexico and identified as Santiago-Galas Clay No. 3.

Additives: Interpolymer of substantially equimolar proportions of ethylene and maleic anhydride and 1% by weight of diallyl ether in its sodium salt form having a specific viscosity of 2.22 alone, soda ash alone, and the interpolymer together with soda ash.

Inter- Soda ash Viscosity Estimated Viscosity Estimated pol mer weight (cp. yield (cp.) yield additive percent (15 min.) (1)101.) (24 hr.) (bbL) lb./ton of clay Example 4 shows that the interpolymers of the invention are also efiective for increasing the yield value of a sub-bentonitic clay, i.e., a calcium bentonite or montmorillonitc, when employed in conjunction with soda ash efiecting a yield almost three times better than that which can be obtained with soda ash alone.

Tests similar to those described in the foregoing examples have been made with an analogous interpolymer of propylene, maleic anhydride and diallyl ether and have demonstrated that this interpolymer is useful as a clay beneficiating agent. Likewise, comparable results are obtained when employing the isobutylene-maleic anhydridediallyl ether for clay beneficiation.

What is claimed is:

1. A composition of matter consisting essentially of an intimate admixture of a bentonitic clay and a water-soluble interpolymer consisting of substantially equimolar proportions of an olefin having from 2-4 carbon atoms and maleic anhydride and from about 0.1% to about 5% by weight of diallyl other, said interpolymer having a specific viscosity of at least 0.3 and said interpolymer being present in an amount sufficient to increase the yield of said clay.

2. The composition of claim 1 wherein said interpolymer is present in an amount in the range from about 0.1 lb. to about 10 lb. per ton of said clay.

3. A composition of matter consisting essentially of an intimate admixture of a bentonite clay and a Watersoluble interpolymer consisting of substantially equimolar proportions of ethylene and maleic anhydride and from about 0.1% to about 5% by weight of diallyl ether, said interpolymer having a specific viscosity of at least 0.3 and said interpolymer being present in an amount sufiicient to increase the yield of said clay.

4. The composition of claim 3 wherein said interpolymer is present in an amount in the range from about 0.1 lb. to about 10 lb. per ton of said clay.

5. The composition of claim 3 wherein said interpoly. mer has a specific viscosity within the range from about 0.6 to about 3.0 and is present in an amount in the range from about 1.5 lb. to about 3.5 lb. per ton of clay.

6. A composition of matter consisting essentially of an intimate admixture of a sub-bentonitic clay, a watersoluble, ionizable alkali metal compound having an anion capable of reacting with calcium ions to form a waterinsoluble precipitate, said compound being present in an amount from about 1% to about 7% by weight of said clay, and an interpolymer consisting of equimolar proportions of an olefin having from 2-4 carbon atoms and maleic anhydride and from about 0.1% to about 5% by weight of diallyl ether, said interpolymer having a specific viscosity of at least 0.3 and said interpolymer being present in an amount sufiicient to increase the yield of said clay.

7. The composition of claim 6 wherein said interpolymer is present in an amount in the range from about 0.1 lb. to about 10 lb. per ton of said clay.

8. A composition of matter consisting essentially of an intimate admixture of a sub-bentonitic clay, a Watersoluble, ionizable alkali metal compound having an anion capable of reacting with calcium ions to form a waterinsoluble precipitate, said compound being present in an amount from about 1% to about 7%- by weight of said clay, and an interpolymer consisting of equimolar pro portions of ethylene and maleic anhydride and from about 0.1% to about 5% by weight of diallyl ether, said interpolymer having a specificvlscosity-of at least 0.3 and said interpolymer being present in an amount sufficient to increase the yield of said clay.

9. The composition of claim 8 wherein said interpolymer is present in an amount in the range from about 0.1 lb. to about 10 lb. per ton of said clay.

10. A composition vof matter consisting essentially of an intimate admixture of a sub-bentonitic clay, soda ash in an References Cited in the file of this patent UNITED STATES PATENTS 2,702,788 Dawson Feb. 22, 1955 2,718,497 Oldham et a1 .S'ept. 20, 1955 2,948,678 Turner et a1 Aug. 9, 1960 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF AN INTIMATE ADMIXTURE OF A BENTONITIC CLAY AND A WATER-SOLUBLE INTERPOLYMER CONSISTING OF SUBSTANTIALLY EQUIMOLAR PROPORTIONS OF AN OLEFIN HAVING FROM 2-4 CARBON ATOMS AND MALEIC ANHYDRIDE AND FROM ABOUT 0.1% TO ABOUT 5% BY WEIGHT OF DIALLYL ETHER, SAID INTERPOLYMER HAVING A SPECIFIC VISCOSITY OF AT LEAST 0.3 AND SAID INTERPOLYMER BEING PRESENT IN AN AMOUNT SUFFICIENT TO INCREASE THE YIELD OF SAID CLAY. 